1. Field of the Invention
This invention relates to the field of torque converters that produce hydrodynamic driving connection between input and output members. The invention particularly relates to such torque converters used to connect an engine to an automotive transmission.
2. Description of the Prior Art
German Offenlegungsschrift No. 23 50 600 describes a hydrodynamic torque converter having a pump wheel, a turbine wheel driven from the pump wheel, and a guide wheel having a variable blade row on the guide wheel. The adjustment of the variable blade row occurs automatically and is actuated by pressure forces developed by the circulating fluid against the action of a restoring spring.
The blades of the guide wheel pivot on radially directed pivot pins, actuated by pivot arms bent at an angle and supported on an axially movable setting ring, and concentric cup springs positioned behind the ring. The position of the springs is selected such that the torque transmitted through the torque converter by the circulating hydraulic fluid flow when the torque converter is stalled, as when starting the motor vehicle from rest, opens the blade row of the guide wheel.
The torque performance figure is changed by pivoting the guide wheel blades such that the starting speed at full load is low, the creeping moment at idle speed is small, and the speed ratio at which the coupling point occurs and overall efficiency are acceptable. However, this torque converter is relatively complicated and the cost of manufacture and assembly is high.
German patent No. 25 05 092 describes a hydrodynamic torque converter having a guide wheel supported on one-way clutch wherein the direction of the fluid flowing between the blade rows of the entrance of the guide wheel is set by the torque exerted by the fluid against the force of a spring. The blades of the guide wheel rotate to adjust the opening. The blade row of the guide wheel is open at the starting point at full load, i.e., at the stall point, and the converter performance number in this instance is high. However, because the opening of the blade row of the guide wheel is almost closed in the idle condition, the corresponding converter performance number and creeping moment are small. This torque converter is complicated and expensive in design because the blades of the guide wheel are rotatably mounted to adjust the opening between the blade rows.
German Auslegeschrift No. 19 56 244 describes the use of a blade row of a guide wheel, which is divided into at least two annular members that are radially divided along a circle and rotate relative to one another about approximately half a blade pitch. The two annular members described in this document are actuated by a hydraulic cylinder located outside the torque converter.